The present invention relates to medical instrument insertion and removal tools, and more particularly to a medical device impacting tool adapted to apply a force to a medical device used during orthopedic surgery.
Advancing age, as well as injuries, can lead to changes in the various bones, discs, joints and ligaments of the body. In particular, these changes can manifest themselves in the form of damage or degeneration of an intervertebral disc, the result of which is mild to severe chronic back pain. Intervertebral discs serve as xe2x80x9cshockxe2x80x9d absorbers for the spinal column, absorbing pressure delivered to the spinal column. Additionally, they maintain the proper anatomical separation between two adjacent vertebra. This separation is necessary for allowing both the afferent and efferent nerves to exit and enter, respectively, the spinal column.
Treatment for a diseased or damaged disc can involve the removal of the affected disc and subsequent fusion of the opposing vertebra to one another. Spinal fusion consists of fusing the adjacent vertebrae through the disc space (the space previously occupied by the spinal disc interposed between the adjacent vertebral bodies). Typically, a fusion cage and/or bone graft is placed into the disc space to position the vertebrae apart so as to create more space for the nerves, to restore the angular relationship between the adjacent vertebrae to be fused, and to provide for material that can participate in and promote the fusion process.
Several different tools have been developed to facilitate the preparation of the adjacent vertebral bodies, as well as the subsequent placement of an implant between adjacent bone structures. Typically, prior to insertion of an implant, bone preparation tools are used to prepare the bone surfaces of the adjacent vertebrae. Mallets are often used to apply an impacting force on a medical tool, such as a chisel, to remove bone from a vertebral body. Mallets are also commonly used to insert an implant, and to remove tools positioned between adjacent vertebrae. While mallets are effective, the impacting force must be axially applied to avoid misalignment of the prosthesis, or the inadvertent removal of bone. Moreover, the force applied must be sufficiently accurate to avoid damage to the vertebrae.
To overcome some of these problems, slaphammers have been developed and are widely used in orthopedic procedures to apply an impacting force on various tools used during surgery. However, most slaphammer designs still have several drawbacks. Current slaphammers tend to be very large and heavy, and are thus difficult to handle. Exceptional care must be exercised while using these instruments to prevent injury to the patient and/or the surgeon. In particular, the surgeon""s hands can be pinched between the hammer portion of the instrument and the hammer stops. Moreover, the size and weight of the slaphammer can make it very difficult for the surgeon to maintain a steady hand. The size and weight can also result in problems with storage and cleaning.
Accordingly, there remains a need for a more compact, lightweight slaphammer device which can be safely and effectively used to apply an impacting force to a medical tool.
The present invention provides a medical instrument impacting tool which is useful to accurately and safely apply a force to a medical instrument and, in particular, to a tool used during spinal and/or orthopedic surgery. The instrument is designed to provide a safe and accurate procedure for applying a force to a medical device, while minimizing the risk of injury to the patient or to the surgeon""s hands during use. The impacting force can be directed to insert or withdraw a medical tool from a location in a patient""s body, to prepare an implant site using a broaching device or similar bone preparation device, or to insert an implant between adjacent bone structures. In addition, the compact design of the instrument provides for ease and accuracy of use, as well as ease of cleaning and storage.
In general, the medical instrument impacting tool includes a hollow tube, a mass slidably disposed within the hollow tube, and a handle mated to the mass and slidably movable between a first, distal position and a second, proximal position. The mass, which is slidably disposed within the tube, is mated to the handle such that movement of the handle causes movement of the mass. The instrument also includes a connector element formed on the distal end of the tube and adapted to mate with a medical instrument. The connector element can be, for example, an elongate shaft extending from the distal end of the cylindrical tube and having a T-connector or other similar type of mechanical connector formed on the distal end thereof to mate with a medical instrument.
In one embodiment, the hollow tube includes outer and inner surfaces, a proximal end, and a distal end, and the handle includes a distal end, a proximal end, and a bore formed therein. The handle can be slidably disposed around the hollow tube, or alternatively, it can be positioned proximal to the hollow tube. The tube can be cylindrical and the outer surface of the mass can slidably engage the inner surface of the cylindrical member. This allows the handle to be spaced apart from the cylindrical tube as it travels between the first and second positions. As a result, movement of the mass is only limited by friction between the mass and the tube. The inner diameter of the handle can be greater than the outer diameter of the cylindrical tube. The instrument can also include an elongate rod disposed within the bore of the handle for mating the distal end of the handle to the mass.
In another embodiment, the handle is positioned adjacent to, or along the side of, the hollow tube. A slot extends between the proximal and distal ends of the hollow tube and includes a proximal end and a distal end. A rigid connector element extends through the slot and mates the handle to the mass. The rigid connector element is slidably movable between the proximal and distal ends of the slot.
In other aspects, the instrument can include a first end cap disposed on the distal end of the cylindrical member, and a second end cap disposed on the proximal end of the cylindrical member. The second end cap can include an aperture formed therein for slidably receiving the elongate rod. In use, movement of the handle from the first position to the second position to impact the proximal end of the tube is effective to cause the mass to apply a proximally directed force to the cylindrical tube, and movement of the handle from the second position to the first position to impact the distal end of the tube is effective to cause the mass to apply a distally directed force to the cylindrical tube.